skip the mani's. Of the two DP options you listed, I would go with labree. 2.5" DP's won't "suck power out of the set up", they just won't free as much power up.
Why would your mechanic need to "fab up" some test pipes? There are plenty of cheap options from TT.NET vendors as well as in the classies here.
If price is not as big of an issue, Mike Smith mani's and SZ 3" expansion DPs are the way to go. I'm assuming you already have a 3" cat back ready to go?